function search(keyword, url) {
    if (url && url.length > 0) {
        return searchUrl(url);
    }
    return searchUrl('https://www.pianba.net/so/-------------.html?wd=' + keyword + '&submit=');
}
function searchUrl(url) {
    return fetch(url).then((response) => {
        const text = response.text();
        return text;
    });
}